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Ultracold Quantum Gases Group

Welcome to the ultracold quantum gas research group at Aarhus University!

In our research we investigate the properties of atomic gases at extremely low temperatures. This allows us to understand the fundamental quantum mechanical behaviour of these many particle systems.


Jan Arlt

New grant: Experiments with Quantum Test Beds

Jan Arlt has recieved a grant from VILLUM FONDEN valued at DKK 4.7 million. View more details here. (01/2016)

Romain working in the lab

Congratulations to Romain!

On the 14th of January, Romain C. G. F. Müller successfully defended his PhD thesis "A new experiment to probe and manipulate quantum systems". The assessment committee consisted of Prof. Leticia Tarruell from ICFO Barcelona and Prof. Henning Moritz from the University of Hamburg. He will carry on his scientific work by continuing in the group as a postdoctoral researcher.

scienceathome.org also did an interview with Romain. (01/2016)

Hilbert space gymnastics

Time limited optimal dynamics beyond the Quantum Speed Limit

Phys. Rev. A 92, 062106

The quantum speed limit sets the minimum time required to transfer a quantum system completely into a given target state. At shorter times the higher operation speed results in a loss of fidelity. Here we quantify the trade-off between the fidelity and the duration in a system driven by a time-varying control. The problem is addressed in the framework of Hilbert space geometry offering an intuitive interpretation of optimal control algorithms. This approach leads to a necessary criterion for control optimality applicable as a measure of algorithm convergence. The time fidelity trade-off expressed in terms of the direct Hilbert velocity provides a robust prediction of the quantum speed limit and allows one to adapt the control optimization such that it yields a predefined fidelity. The results are verified numerically in a multilevel system with a constrained Hamiltonian and a classification scheme for the control sequences is proposed based on their optimizability. (12/2015)

Immiscible 39K and 87Rb condensates in time of flight

First paper from the MIX lab published!

Tunable dual-species Bose-Einstein condensates of 39K and 87Rb

Phys. Rev. A 92, 053602

We present the production of dual-species Bose-Einstein condensates of 39K and 87Rb. Preparation of both species in the |F=1,mF=−1> state enabled us to exploit a total of three Fesh\-bach resonances which allows for simultaneous Feshbach tuning of the 39K intraspecies and the 39K-87Rb interspecies scattering length. Thus dual-species Bose-Einstein condensates were produced by sympathetic cooling of 39K with 87Rb. A dark spontaneous force optical trap was used for 87Rb, to reduce the losses in 39K due to light-assisted collisions in the optical trapping phase, which can be of benefit for other dual-species experiments. The tunability of the scattering length was used to perform precision spectroscopy of the interspecies Feshbach resonance located at 117.56(2)G and to determine the width of the resonance to 1.21(5)G by rethermalization measurements. The transition region from miscible to immiscible dual-species condensates was investigated and the interspecies background scattering length was determined to 28.5a0 using an empirical model. This paves the way for dual-species experiments with 39K and 87Rb BECs ranging from molecular physics to precision metrology. (11/2015)

Nils after winning

Nils wins Researchers Battle 2015

In a dissemitation contest with other PhD students from Aarhus University, Nils presented his reasearch in ultracold atoms for a general audience in just four minutes. Through a vote from the audience and three referees, he won the contest! Read more here where au.dk covered the event. (09/2015)

Congratulations to Mirek!

On the 23rd of September, Miroslav Gajdacz successfully defended his PhD thesis "Stabilizing production of atomic clouds". The assessment committee consisted of Prof. Dr. Christiane Koch from University of Kassel and Prof. David Guéry-Odelin from the University of Toulouse. He will carry on his scientific work by continuing in the group as a postdoctoral researcher. (09/2015)

Congratulations to Lars!

On the 22nd of September, Lars Johann Wacker successfully defended his PhD thesis "Few-body physics with ultracold potassium rubidium mixtures". The assessment committee consisted of Prof. Selim Jochim from Heidelberg University and Dr. Steven Knoop from the University of Amsterdam. He will carry on his scientific work by continuing in the group as a postdoctoral researcher. (09/2015)

Congratulations to Danny!

Danny Birkmose succesfully defended his Master thesis "Investigation of Dual Species Bose Einstein Condensates". Danny has been working as a master student on the MIX experiment for the last year. (08/2015)

The ultracold atom reservoir

A continuously pumped reservoir of ultracold atoms

Typical sources of ultracold atoms operate with a considerable delay between the delivery of ensembles due to sequential trapping and cooling schemes. Therefore, alternative schemes for the continuous generation of ultracold atoms are highly desirable. Here, we demonstrate the continuous loading of a magnetic trap from a quasi-continuous atom beam. We achieve a steady state with 3.8x107 magnetically trapped atoms and a temperature of 102uK. The ensemble is protected from laser light sources, a requirement for its application in metrological tasks or sympathetic cooling. The continuous scheme is robust and applicable to a wide range of particles and trapping potentials.

In addition, this work received media attention at 2physics and at Physicsworld.com. The paper can be found here. (07/2015)

Jan Arlt

New grant: Few-body Quantum Physics with Ultracold Atoms

Jan Arlt has recieved a grant from The Danish Council for Independent Research valued at DKK 2.6 million. View more details here (in danish). (05/2015)

Goodbye to Nils

After finishing his PhD and spending a year as a postoctoral reasearcher, Nils Winter is leaving the group to go back to Germany, where he will persue a career outside of academia. We wish him the best of luck in all future endeavours! (01/2014)

Congratulations to Robert!

On the 15th of January Robert Heck successfully defended his progress report "Creation of 87Rb Bose-Einstein Condensates in Different Trap Configurations". The external examiner were Jörg Helge Müller from the Niels Bohr Institute. (01/2015)


Our research is supported by:

The Danish National Research Foundation within the Center for Quantum Optics (QUANTOP).

Henvendelse om denne sides indhold: 
Revideret 26.01.2016

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Institut for Fysik og Astronomi
Aarhus Universitet
Ny Munkegade 120
8000 Aarhus C

E-mail: phys@au.dk
Tlf: 8715 0000 (Aarhus Universitets hovednummer)
Fax: 8612 0740

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Nyttige numre

CVR-nr: 31119103

Momsnummer/VAT: DK 3111 9103
(alle internationale køb)

P-nr: 1009828059

EAN-nr: 5798000419872

Stedkode: 2902

Enhedsnummer: 5200